1. Field of the Invention
The present invention relates generally to an anionic polymerization process of .omega.-lactum and, more particularly, it relates to an anionic polymerization process of .omega.-lactum using as a promotor an N-substituted ethyleneimine derivative having the general formula ##EQU2## WHEREIN R represents an organic group as hereafter defined, and n is 2 or 3.
2. Description of the Prior Art
As a polymerization process for lactam, a process in which a lactam is polymerized by heating it to a high temperature for a along period of time in the presence of water, a mineral acid, a fatty acid, or an amine is well-known. Furthermore, an anionic polymerization process wherein a strong basic material is employed as the catalyst is also well-known.
It is known that alkali metals; alkaline earth metals; the hydroxides, hydrides, carbonates, or organic compounds of those metals; organoaluminum compounds such as triethylaluminum and lithium aluminum hydride; and organomagnesium compounds such as a Grignard reagent; are effective as the catalyst for the aforesaid anionic polymerization.
However, in the case of using the above-described catalyst individually in the ring-opening polymerization of lactam as described above, it is required in polymerizing the lactam to heat the reaction system to high temperatures above 200.degree. C for a few hours and also it is further required in obtaining the polymer of lactam having a higher polymerization degree with a higher polymerization yield to heat the reaction system to a higher temperature for a longer period of time than above.
It is, however, possible to obtain a polymer or a polyamide having a higher polymerization degree with a higher polymerization yield at low temperatures below 200.degree. C in quite a short period of time by using a proper polymerization promotor together with the catalyst and thus it is quite effective for the anionic polymerization of lactam to use the promotor together with the catalyst as described above.
As such a promotor, acyl chlorides, acyl anhydrides, acylimides, carbodiimides, organic isocyanates, and other various acylating agents and acyl compounds are well-known. However, these known promotors tend to be deteriorated by moisture in the air to lose their activity and thus these compounds must be handled carefully. Moreover, the use of isocyanate compounds requires various precautions due to the toxicity thereof. Also, an acid chloride tends to react with water to form hydrochloric acid and an organic acid, which results in reducing the activity of the acid chloride as a promotor as well as adversely influences the polymerization of lactam.
Furthermore, when a lactam is polymerized using such a known promotor, a polymer having an undesirable color is frequently produced, for example, when an organic carboxylic acid anhydride is used as the promotor in the polymerization of lactam, only dark brown polymers are obtained.